Generic USB Display Driver "GUD" Slated For Linux 5.13
The open-source Generic USB Display Driver when paired with a proper USB gadget driver can be used for projects like do-it-yourself USB-to-HDMI/SDTV/DPI display adapters with boards like the Pi Zero. The GUD driver is indeed "generic" and can be adapted for various USB adapters. Longtime open-source developer Noralf Trønnes who has been working on GUD for months has been doing much of his work with the Pi Zero.
This effort has been in the works for quite a while but now has made it into DRM-Misc-Next and was part of today's PR going to DRM-Next ahead of the Linux 5.13 merge window kicking off in late April.
More details on the GUD driver can be found via the project's Wiki. The GUD kernel driver in its current form is around twenty five hundred lines of code. For enhancing the display performance over USB, LZ4 compression is supported if the device supports it. GUD does support plane rotation and connector TV properties. There is also support for backlight handling and other features.
The GUD driver is intentionally MIT licensed for opening it up and encouraging porting to other platforms like the BSDs.
Below is a video from last year of the GUD driver in action with Raspberry Pi hardware: